EASTERN BOX TURTLE ASSESSMENT
revised March 31, 2000
Prepared by: Charles S. Todd
Maine Department of Inland Fisheries and Wildlife Wildlife Division Wildlife Resource Assessment Section Endangered and Threatened Species Group
EASTERN BOX TURTLE ASSESSMENT
TABLE OF CONTENTS
Page INTRODUCTION...... 3
NATURAL HISTORY...... 4 Description...... 4 Distribution...... 6 Taxonomy...... 6 Habitat, Diet, and Movements ...... 8 Winter Hibernation...... 11 Reproductive Ecology...... 12 Survival and Longevity ...... 14
MANAGEMENT ...... 15 Regulatory Authority ...... 15 Past Goals and Objectives ...... 19 Past and Current Management...... 19
HABITAT ASSESSMENT...... 20 Historic Trends ...... 20 Current Assessment ...... 20 Projections...... 21
POPULATION ASSESSMENT...... 22 Historic Trends ...... 22 Current Assessment ...... 22 Projections...... 25 Limiting Factors ...... 25
USE AND DEMAND ASSESSMENT ...... 27 Historic Trends ...... 27 Current Assessment ...... 28 Projections...... 29
SUMMARY AND CONCLUSIONS ...... 30
LITERATURE CITED ...... 32
APPENDIX1. Table 1. Historic and recent records of box turtles in southern Maine, by county and township...... 41
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INTRODUCTION
Since 1968, the Maine Department of Inland Fisheries and Wildlife (MDIFW) has
developed and refined wildlife species assessments to formulate management goals,
objectives, and strategic plans. Assessments are based upon available information and
the judgments of professional wildlife biologists responsible for individual species or
groups of species. This document represents the first planning effort by MDIFW for
eastern box turtles (Terrapene carolina carolina), a reptile designated an “endangered species” in Maine.
Assessments provide the background for species planning initiatives. A “Natural
History” section reviews biological characteristics of the species useful to understanding
its status. The “Management” section recaps previous actions, strategic plans, relevant
rules, and regulatory authority. Historic, current, and projected future conditions for the
species are discussed individually for “Habitat,” “Population,” and “Use and Demand”
analyses. The major points of an assessment appear in a “Summary and Conclusions.”
Owing to the extreme scarcity of eastern box turtles in Maine and limited
information about them, this assessment draws heavily on studies and insights from
other regions. Mark McCollough prepared two earlier drafts of this assessment.
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NATURAL HISTORY
Description
The eastern box turtle is a small terrestrial turtle with a high-domed carapace and unique plastron (Figure 1). The carapace (top shell) has a slight median keel and is steeply sloped on the rear margin. It is brown-colored with variable yellow, orange, or olive patterns of radiating lines, spots, bars, or irregular blotches on each scute. An adult's carapace is 10 - 20 cm long (Smith 1961, Conant and Collins 1991). Maximum size is attained at ages between 12 - 20 years (Nichols 1939). Individuals from the
North, especially New England, are larger than others (Milstead 1969, Klemens 1993).
The plastron (bottom shell) is tan to dark brown and variably mottled with yellow.
A strong hinge on the plastron between the abdominal and pectoral scutes enables it to shut tightly against the carapace after withdrawing legs, head, and tail. This response is common among wild turtles, but not those which are pets. It seals soft body parts from external threats, an adaptation which accounts for the common name “box turtle.”
The skin of eastern box turtles is black to reddish-brown with yellow or orange spots and streaks. Head markings vary. The upper jaw has a terminal hook and usually lacks a notch. Sexual dimorphism is marked (Ernst and Barbour 1972, Conant and Collins 1991, Klemens 1993). Most adult males have red or orange eyes; concave plastron; short, stocky, and considerably curved hind feet; long, thick tails; and relatively greater shell width and height than females. Females generally have yellowish-brown eyes; a flat plastron; longer, more slender, and straighter hind legs; and a shorter, slighter tail with the anus located more anterior. Hatchlings lack bright coloration.
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Figure 1. An eastern box turtle (Terrapene carolina carolina).
Figure 2. Range of the eastern box turtle (Terrapene carolina carolina, solid shading), other eastern box turtle subspecies (Terrapene carolina, crosshatched), and ornate box turtles (Terrapene ornata, hatched areas) across North America.
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Distribution
Box turtles occur only in North America (Conant and Collins 1991). Collectively,
the two species native to the United States (see “Taxonomy”) range from the Atlantic
Ocean to the Rocky Mountains. The species addressed in this assessment, the eastern
box turtle (Terrapene carolina), reaches its western limits and overlaps with a
midwestern species, the ornate box turtle (Terrapene ornata) in Wisconsin, Illinois,
Missouri, Kansas, Oklahoma, and Texas. Eastern box turtles are broadly distributed in
the eastern and central U. S. from northern states nearly abutting the Canadian border
southward to the Gulf coast and northern Mexico (Figure 2).
The subspecies native to Maine, T. c. carolina, occurs broadly over the Atlantic
seaboard from southern Maine to northern Florida. It ranges westward through Illinois,
Kentucky, Tennessee, and Mississippi to the Mississippi River. A crucial perspective to
Maine, its northern limits, are traditionally depicted as: southern Maine; southeastern portions of New Hampshire, Vermont, and New York; across most of Pennsylvania and
Ohio; central Michigan; and extreme southeastern Wisconsin (Behler and King 1979).
Three other subspecies of eastern box turtles live in the South or Midwest.
Taxonomy
Approximately 250 species of turtles and tortoises belong to 12 different families
in the taxonomic order Testudines (Tyning 1990). Box turtles (genus Terrapene) are members of the family Emydidae which contains the largest number of living turtle species. Commonly called the family of freshwater and marsh turtles, its members occur on all continents except Australia and Antarctica (Carr 1952). This family is
6 EASTERN BOX TURTLE ASSESSMENT
represented by 33 species in the U. S. and Canada (Collins 1997). All are aquatic or semiaquatic except for the two species of Terrapene. Although they resemble tortoises
(family Testudinidae), box turtles have freestanding toes and some toe webbing: traits shared among all emydid turtles (Tyning 1990).
The genus Terrapene occurs exclusively in North America. Phalangeal formulae
distinguish species and subspecies of Terrapene (Baur 1891, 1893; Taylor 1895; Minx
1992). The two species living in the U. S. are visually distinct. The ornate box turtle, T.
ornata, is identified by distinct, bright colors on a keelless, low, and flattened carapace.
The carapace of an eastern box turtle, T. carolina, is keeled and high-arched. They
may cross breed in areas of range overlap in the Midwest (Smith 1961). Two others
species live in Mexico: T. nelsoni and T. coahuila. At least 2 fossil species of
Terrapene are reported from the southeastern U. S. (Hay 1907, Ernst et al. 1998).
There are 6 extant subspecies of T. carolina. (Collins 1997). Two live in northern
Mexico: T. c. mexicana and T. c. yucatana. Interbreeding among the four subspecies
resident in the U. S. may occur where ranges overlap (Figure 2, Milstead 1969):
T. c. carolina (Linnaeus) - The eastern box turtle is the subspecies that occurs in Maine. It is differentiated by a brightly marked, short, and broad carapace with the marginals flared only slightly and nearly vertical at the posterior (Ernst and Barbour 1972). T. c. major (Agassiz) - The Gulf Coast box turtle ranges along the coastal plain of the Gulf of Mexico from the Florida panhandle to eastern Texas. Its carapace often lacks yellowish markings, is elongate, and may exceed 20 cm in length. T. c. triunguis (Agassiz) - The three-toed box turtle ranges from Kansas and Missouri south to Texas, Alabama, and Georgia. It has 3 toes on the hind foot and an obscurely marked, tan - olive carapace. T. c. bauri (Taylor) - The Florida box turtle is restricted to peninsular Florida and the Keys. It also has 3 toes on the hind foot, but the carapace has a bright pattern of radiating lines. It has two characteristic stripes on each side of the head.
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Habitat, Diet, and Movements
Habitats of eastern box turtles are generally terrestrial: woodlands, field edges,
pastures, and thickets. Despite their terrestrial nature, they are never far from water
(Allard 1948). Young box turtles are thought to be semiaquatic (Ernst and Barbour
1972), and adults are occasionally observed swimming in slow-moving streams and
ponds. Sandy, well-drained soils typify most box turtle settings (Klemens 1993).
Regional variations are evident. In New York (Madden 1975) and Connecticut
(Klemens 1993), box turtles favor areas of high habitat diversity such as “old fields” and
deciduous forest ecotones (e.g., power line corridors). They appear most often in open
deciduous forests and mountain slopes in Massachusetts (DeGraaf and Rudis 1983).
Bottomland forests are frequented in Maryland (Stickel 1950, 1989) and Pennsylvania
(Strang 1983). Indiana woodlands dominated by maples were favored relative to those in upland settings like oak stands, steep-sided gorges, and utility corridors (Williams and
Parker 1987). Schwartz and Schwartz (1974) noted a decrease in densities of box turtles going from heavily wooded to more open areas in Missouri.
Box turtles are omnivorous. Stomach contents of 40 individuals examined by
Surface (1908) contained both animal materials (80%) and plant materials (62%).
Young turtles are chiefly carnivorous and become more herbivorous with age (DeGraaf
and Rudis 1983). Box turtle stomach contents (by volume) were 60% snails, 15%
crayfish, and 12.5% plant material in one Kentucky study (Barbour 1950) and 52.5%
snails and slugs, 10% caterpillars, 10% mushrooms, 4% beetles, and 3.5% centipedes
in another (Bush 1959). Roots, stems, leaves, fruits, and some seeds are all eaten.
Invertebrate foods include slugs, snails, earthworms, spiders, crayfish, millipedes,
8 EASTERN BOX TURTLE ASSESSMENT grasshoppers, flies, beetles, ants, termites, cicadas, caterpillars, insect grubs, and maggots. Box turtles eat vertebrates such as small fish, salamanders, frogs, toads, lizards, and some snakes. Box turtles also consume carrion (Ernst and Barbour 1972).
Box turtles are ectothermic. Their behavior, movements, and habitat selection are dictated largely by ambient temperature and moisture. Three-toed box turtles in
Arkansas maintained optimal conditions by selecting different microhabitats within their home range each day (Reagan 1974). They moved into microhabitats to keep body temperatures between 29 - 38º C. Ornate box turtles in Wisconsin utilize a broader, lower range of body temperatures than those in southern states (Ellner and Karasov
1993). Therefore, thermal preferences and activity periods vary regionallly. This adaptation defies the generalization that turtles are strictly passive to thermal gradients across their range. Thermal conditioning of hatchlings may be influential (Curtin 1998).
Latitudinal variations and patterns of microhabitat selection for thermoregulation have not been similarly examined in eastern box turtles. Most depict them as
“indifferent” towards thermoregulation (Madden 1975, Adams et al. 1989), although behavioral adjustments and specific microhabitats minimize their exposure to thermal extremes. Eastern box turtles avoid excessive solar radiation in summer and maintain body temperatures near the thermal regime of shaded settings (Russo 1972). They visit shallow wetlands in summer to cool themselves and obtain water. Basking sites
(openings in the forest canopy) may be repeatedly used for warming when necessary.
Initial, meticulous studies of eastern box turtles in Maryland (Stickel 1950) and
Tennessee (Dolbeer 1969) utilized a “trailing device:" a spool of thread attached to the turtle that unwinds during its daily course of movements (Claussen et al. 1997). Box
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turtles proved to be strictly diurnal and most active during high humidity periods, often in
early morning or after thunderstorms to avoid hot summer temperatures (Dodd et al.
1991, Klemens 1993). At night, box turtles create "forms," cavities in leaves, debris, or
soil often under dense cover. In spells of dry, or unusually hot or cold weather, a turtle may stay in its form for days or weeks.
Most box turtles are sedentary. Home ranges of T. c. carolina on Long Island,
NY had diameters <230 m and changed little over the years (Madden 1975), although one wandered more than 800 m (Nichols 1939). Smaller home ranges are reported for this subspecies in Tennessee: mean = 76 m diameter (Dolbeer 1969). Average home ranges were 1.13 ha (females) - 1.20 ha (males) in Maryland (Stickel 1950, 1989) and
10 ha (females) - 12 ha (males) in Michigan (Weatherby 1996). Home ranges of T. c. triunguis differed by age in Missouri (Schwartz and Schwartz 1974). Some individuals are transients and do not establish home ranges (Kiester et al. 1982).
Box turtles are not territorial. All ages and both sexes coexist well. Individuals
maintain stable home ranges for periods of up to 14 years (Stickel 1989). Movements
of mated partners overlap broadly. Habitat use is not random; certain paths and activity
centers may be used repeatedly (Weatherby 1996). Occasional forays do occur outside
a home range, especially by females searching for nest sites (Stickel 1950).
Homing tendencies of box turtles are widely reported. Most adults (89.5%) found
their home ranges after displacements of 800 -1200 m (Nichols 1939). Gould (1957)
found that 50% moved homeward instantly when released up to 9000 m away. Long,
unidirectional movements are typical (Lemkau 1970). Geomagenetism and solar cues
contribute to their homing skills (DeRosa and Taylor 1980, Mathis and Moore 1988).
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Winter Hibernation
Box turtles overwinter on land and hibernate when mean ambient temperatures
drop below 16° C (Dolbeer 1971). Hibernation often follows first killing frosts (Schwartz
and Schwartz 1974). Exposure to sudden temperature drops is a liability of terrestrial
hibernation that may require longer inactivity than aquatic turtles. In Connecticut, box
turtles are active between April 25 and October 22 (Klemens 1993). Hibernation
periods of eastern box turtles averaged 141 - 142 days in both Ohio (Claussen et al.
1991) and New York (Madden 1975), and up to 168 days in Maryland (Stickel 1989).
Most box turtles hibernate in their summer home range (Dolbeer 1971, Schwartz
and Schwartz 1974, Stickel 1989). No more than four are known in a hibernaculum
(Ernst and Barbour 1972). In Oklahoma, three-toed box turtles hibernate with snapping
turtles (Chelydra serpentina) and ornate box turtles (Carpenter 1957). Three-toed box
turtles in Kansas often use communal hibernacula (Metcalf and Metcalf 1979). Many
hatchling turtles survive brief freezing exposure (Packard at al. 1999) since they
overwinter in the nest (Ernst and Barbour 1972, Behler and King 1979).
Hibernacula used by older turtles are typically under cover of logs, shrubs, brush piles, or leaf litter (Carpenter 1957). When entering hibernation, box turtles burrow into loose soil, sand, detritus, mud of ponds or streams, mammal burrows, or stump holes.
Many use one hibernaculum in successive winters (Madden 1975, Stickel 1989). Some do not exhibit this fidelity and venture beyond their summer range (Gaines et al. 1996).
Hibernacula of eastern box turtles in Ohio were in woodland edges <10 m from
grasslands at depths averaging only 4 - 5 cm (Claussen et al. 1991), but they may
burrow up to 48 cm deep as the soil temperature drops (Cahn 1933, Dolbeer 1971).
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Their orientation inside winter dens changes with air and soil temperatures (Congdon et
al. 1989) and during spring emergence (Wetmore 1920, Allard 1935).
Many cite anecdotal evidence of high winter kill by freezing (Cahn 1933; Allard
1935, 1948; Neill 1948; Schwartz and Schwartz 1974; Metcalf and Metcalf 1979), but
the extent of this phenomenon is debated (Grobman 1990). Losses likely occur only
after prolonged subzero temperatures in hibernacula (Claussen et al. 1991). Warm
spells in winter or early spring may cause premature emergence, and some are killed by
rapid temperature declines (Ernst and Barbour 1972). Others may enter a new
hibernation site (Allard 1935, Carpenter 1957). Change of winter burrows may occur
early or late in the hibernation season (Congdon et al. 1989). Emergence followed five
consecutive days of underground temperatures >7° C in Missouri (Grobman 1990).
Recent studies demonstrate that eastern box turtles can tolerate nearly complete
freezing for periods of time during the winter (Costanzo and Claussen 1990; Storey and
Storey 1988, 1992; Storey et al. 1993) . Core body temperatures as low as -3.6º C,
freezing periods of up to 73 hours, and ice contents as high as 58% of total body water are recorded for the species. Physiological adjustments by the liver boost the glucose content of vital organs and minimize extracellular ice formation (Storey 1990).
Reproductive Ecology
Box turtles mature at ages of 4 - 5 years in Kentucky (Ernst and Barbour 1972), 5
- 7 years in Pennsylvania (Shaffer 1991), 5 - 10 years in Indiana (Minton 1972), and approximately 20 years in the Northeast (Klemens 1993). At earliest maturity, carapace
length is 10 - 13 cm (Carr 1952). Males grow more rapidly than females, and growth
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rates lessen with advancing age (St. Clair 1998, Stickel and Bunck 1989).
Courtship and mating occur throughout warm periods from April into fall months
(Stickel 1989). Peak sperm production occurs in July and August (Altland 1972). After
ritualized mating behavior (Cahn and Conder 1932, Evans 1953), the male mounts a
female and intromission occurs. A male can die after copulation by falling backwards in
places where it cannot right itself (Allard 1935). Females may not breed every year
(Legler 1960, Doroff and Keith 1990), but can store sperm and lay viable eggs for up to
4 years after mating (Ewing 1943). Egg output of western box turtles (T. ornata luteola) varies in response to environmental stresses (Nieuwolt-Dacanay 1997).
Nesting occurs from June to July in New England (DeGraaf and Rudis 1983).
Females are very mobile prior to egg laying and may extend their home range (Stickel
1950, 1989). At such times, box turtles are often seen crossing roads (DeGraaf and
Rudis 1983). Most nests are initiated at twilight and completed after dark (Ernst and
Barbour 1972). T. c. carolina normally nests in cavities dug 8 cm below the surface in sandy or loamy soil with little vegetation or overhead cover (Allard 1948). Females put
soft litter around eggs before covering a nest with excavated soil (Messinger and Patton
1995). Some use the same nest location for several years in succession (Stickel 1989).
Clutch size varies from 3 to 9 eggs and averages 4 - 5 (Ernst and Barbour 1972).
Eggs are elliptical, thin-shelled, and <3 cm long (Shaffer 1991). Ewing (1943) reported
a fertility rate of 78.6%. In New England, there are no records of multiple clutches in a
year (Klemens 1993) as occurs in southern regions (Ewing 1935, Reimer 1981).
Incubation period is temperature dependent and is influenced by microhabitat
(i.e., soil, air temperature, solar exposure) of the nest site. Clutches at the same site in
13 EASTERN BOX TURTLE ASSESSMENT
Connecticut hatched after incubations intervals of 100 days one year and 123 days the
next (Klemens 1993). Eggs generally require at least 87 - 89 days (overall range = 69 -
136 days) before hatching (Allard 1935). Sex determination in box turtles may be
temperature dependent as in some other turtles (Vogt and Bull 1982).
Survival and Longevity
Most terrestrial turtles exhibit high hatchling and juvenile mortality that is offset by
unusual longevity of a few individuals (Auffenberg and Iverson 1979). Juveniles
comprised >15% of a healthy population in Florida (Dodd et al. 1991). Survival to 20
years of age was 15.6 - 36.0% (males) and 13.8 - 15.6% (females) among eastern box
turtles in Indiana (Williams and Parker 1987). Patterns were similar in Maryland (Stickel
1978). Yahner (1974) cited 79.5% annual survival in Tennessee. Nearly identical rates
(81 - 82%) were found in ornate box turtles from Wisconsin (Doroff and Keith 1990) and a study of three-toed box turtles in Missouri (Kiester et al. 1982). Substantially lower survival was noted in another Missouri study (Schwartz and Schwartz 1974), as well as among ornate box turtles in Texas (Blair 1976) and Kansas (Metcalf and Metcalf 1985).
Longevity of box turtles is legendary. Many live 60 - 80 years (Nichols 1939,
Schwartz and Schwartz 1991), and a few reputedly lived >100 years in New England
(Graham and Hutchinson 1969). Many longevity records are derived from a practice of
people carving a year on the plastron of a captured turtle. One T. carolina marked in
this manner apparently lived 138 years in the wild (Oliver 1955). Causes of death most
often cited among older turtles include human-related losses (e.g., vehicles, mowers,
and farm equipment) and extraction from hibernacula by carnivores (Klemens 1993).
14 EASTERN BOX TURTLE ASSESSMENT
MANAGEMENT
Regulatory Authority
Federal jurisdiction is limited. All box turtles (Terrapene spp.) were added to the
Appendix II of the Conservation on International Trade in Endangered Species of Wild
Fauna and Flora (C.I.T.E.S.) on February 16, 1995 (Levell 1997). Appendix II of this
treaty requires permits for importing or exporting listed species in order to (1) track
international trade amongst 130 participating nations and (2) evaluate such trade as a
threat of extinction. Also, live turtles <10 cm in carapace length and viable turtle eggs cannot be imported, sold, held for sale, or held for distribution except for scientific, educational, or exhibition purposes. Appropriate exhibition does not include the pet trade or any form of export program. This regulation relates to public health concerns from Salmonella transmission to man from turtles (U. S. Food and Drug Administration
21 CFR 1240.62; U. S. Public Health Service 42 CFR 71.52).
Enabling state statutes (12 MRSA Chapter 713) direct MDIFW to "preserve,
protect and enhance the inland fisheries and wildlife resources of the state; to
encourage the wise use of these resources; to ensure coordinated planning for the
future use and preservation of these resources; and to provide for the effective
management of these resources" (§7011). "Wildlife" is defined as "any species of the
animal kingdom, except fish, which is wild by nature, whether or not bred in captivity,
and includes any part, egg, or offspring thereof or the dead body parts thereof" (§7001).
Nevertheless, state law provides only minimal protection for most reptiles. The
first restrictions on take or possession of snakes and most turtles from the wild were
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bans on export, sale, or commercial uses enacted in 1993 (§7471). Wildlife (including
reptiles) may be possessed for other uses in Maine, if appropriate permits are obtained: